Patch "powerpc/eeh: Fix stale cached primary bus" has been added to the 4.4-stable tree

PATCH [email protected] 1 participant 1 message Feb 24, 2016

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Stable branch PowerPC PCI enhanced error handling (eeh) for PowerPC

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2016-02-24 03:54 UTC #0 lore raw

This is a note to let you know that I've just added the patch titled

powerpc/eeh: Fix stale cached primary bus

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
powerpc-eeh-fix-stale-cached-primary-bus.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 05ba75f848647135f063199dc0e9f40fee769724 Mon Sep 17 00:00:00 2001

From: Gavin Shan <[email protected]>
Date: Tue, 9 Feb 2016 15:50:21 +1100
Subject: powerpc/eeh: Fix stale cached primary bus

From: Gavin Shan <[email protected]>

commit 05ba75f848647135f063199dc0e9f40fee769724 upstream.

When PE is created, its primary bus is cached to pe->bus. At later point, the cached primary bus is returned from eeh_pe_bus_get(). However, we could get stale cached primary bus and run into kernel crash in one case: full hotplug as part of fenced PHB error recovery releases all PCI busses under the PHB at unplugging time and recreate them at plugging time. pe->bus is still dereferencing the PCI bus that was released.

This adds another PE flag (EEH_PE_PRI_BUS) to represent the validity of pe->bus. pe->bus is updated when its first child EEH device is online and the flag is set. Before unplugging in full hotplug for error recovery, the flag is cleared.

Fixes 8cdb2833 ("powerpc/eeh: Trace PCI bus from PE")

Reported-by Andrew Donnellan <[email protected]>

Reported-by Pradipta Ghosh <[email protected]>

Signed-off-by Gavin Shan <[email protected]>

Tested-by Andrew Donnellan <[email protected]>

Signed-off-by Michael Ellerman <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 arch/powerpc/include/asm/eeh.h               |    1 +
 arch/powerpc/kernel/eeh_driver.c             |    3 +++
 arch/powerpc/kernel/eeh_pe.c                 |    2 +-
 arch/powerpc/platforms/powernv/eeh-powernv.c |    5 ++++-
 4 files changed, 9 insertions(+), 2 deletions(-)

arch/powerpc/include/asm/eeh.h +1 -0

@@ -81,6 +81,7 @@ struct pci_dn;
 #define EEH_PE_KEEP		(1 << 8)	/* Keep PE on hotplug	*/
 #define EEH_PE_CFG_RESTRICTED	(1 << 9)	/* Block config on error */
 #define EEH_PE_REMOVED		(1 << 10)	/* Removed permanently	*/
+#define EEH_PE_PRI_BUS		(1 << 11)	/* Cached primary bus   */
 
 struct eeh_pe {
 	int type;			/* PE type: PHB/Bus/Device	*/

arch/powerpc/kernel/eeh_driver.c +3 -0

@@ -564,6 +564,7 @@ static int eeh_reset_device(struct eeh_p
 	 */
 	eeh_pe_state_mark(pe, EEH_PE_KEEP);
 	if (bus) {
+		eeh_pe_state_clear(pe, EEH_PE_PRI_BUS);
 		pci_lock_rescan_remove();
 		pcibios_remove_pci_devices(bus);
 		pci_unlock_rescan_remove();

@@ -803,6 +804,7 @@ perm_error:
 	 * the their PCI config any more.
 	 */
 	if (frozen_bus) {
+		eeh_pe_state_clear(pe, EEH_PE_PRI_BUS);
 		eeh_pe_dev_mode_mark(pe, EEH_DEV_REMOVED);
 
 		pci_lock_rescan_remove();

@@ -886,6 +888,7 @@ static void eeh_handle_special_event(voi
 					continue;
 
 				/* Notify all devices to be down */
+				eeh_pe_state_clear(pe, EEH_PE_PRI_BUS);
 				bus = eeh_pe_bus_get(phb_pe);
 				eeh_pe_dev_traverse(pe,
 					eeh_report_failure, NULL);

arch/powerpc/kernel/eeh_pe.c +1 -1

@@ -928,7 +928,7 @@ struct pci_bus *eeh_pe_bus_get(struct ee
 		bus = pe->phb->bus;
 	} else if (pe->type & EEH_PE_BUS ||
 		   pe->type & EEH_PE_DEVICE) {
-		if (pe->bus) {
+		if (pe->state & EEH_PE_PRI_BUS) {
 			bus = pe->bus;
 			goto out;
 		}

arch/powerpc/platforms/powernv/eeh-powernv.c +4 -1

@@ -444,9 +444,12 @@ static void *pnv_eeh_probe(struct pci_dn
 	 * PCI devices of the PE are expected to be removed prior
 	 * to PE reset.
 	 */
-	if (!edev->pe->bus)
+	if (!(edev->pe->state & EEH_PE_PRI_BUS)) {
 		edev->pe->bus = pci_find_bus(hose->global_number,
 					     pdn->busno);
+		if (edev->pe->bus)
+			edev->pe->state |= EEH_PE_PRI_BUS;
+	}
 
 	/*
 	 * Enable EEH explicitly so that we will do EEH check

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/powerpc-eeh-fix-pe-location-code.patch queue-4.4/powerpc-eeh-fix-stale-cached-primary-bus.patch queue-4.4/powerpc-powernv-fix-stale-pe-primary-bus.patch